Preparation:Combine the sifted flour, sugar, baking powder and salt in a large bowl, blend well. Pour in the sour cream and beer and mix thoroughly but do not beat. Grease a 2 1/2 quart baking dish or similar size pan. Preheat oven to 350 degrees. Pour mixture into pan and bake for 40-45 minutes. Remove and brush top with 1 tbsp margarine. Return to oven and bake 15 minutes longer or until browned.